Showing papers in "Advanced Materials Research in 2010"
TL;DR: In this article, the polysaccharide extract conditions using G. amansii were described to maximize the total yields of polymers and their conversion rate into monosugars which are able to be converted into bioethanol.
Abstract: Recently, red seaweed attacks growing interests as 3rd generation biomass due to their notable characteristics e. g. no lignin, high CO2 fixation ability as well as high carbohydrate contents such as galactan and glucan. Seaweed may belong to one of the several groups of multicellular macro algae (the red algae, green algae, and brown algae). The ecology of seaweeds is dominated by two specific environmental requirements, that is the presence of seawater and light sufficient to drive photosynthesis. Seaweed is currently being researched as a potential source of biofuel in the form of bioehtanol. Especially, Gelidium amansii known as one of the red seaweed can be depolymerized to produce mixed monosugars such as glucose and galactose. We describe here the polysaccharide extract conditions using G. amansii to maximize the total yields of polymers and their conversion rate into monosugars which are able to be converted into bioethanol.
73 citations
TL;DR: In this article, the inlet gas temperature and pressure were varied for two different powder morphologies in such a way that the average particle velocity ranged from ~600 to 850 m/s.
Abstract: Ti and Ti-6Al-4V coatings were deposited by cold gas dynamic spray process using nitrogen as propellant gas. For Ti, the inlet gas temperature and pressure were varied for two different powder morphologies in such a way that the average particle velocity ranged from ~600 to 850 m/s. In addition, the nozzle traverse speed was varied. For all conditions, the deposition efficiency, the porosity, and the microhardness were measured. It is shown that the porosity level decreased as the gas temperature and pressure increased, whereas the velocity, deposition efficiency, and microhardness increased. Furthermore, it is observed that a lower nozzle traverse speed engendered a softer coating. The coating adhesion on a grit 24 Al2O3 blasted mild steel surface was established to be greater than 78.8 MPa. In addition, a Ti-6Al-4V coating was produced and was determined to be slightly more porous compared to a CP Ti coating.
72 citations
TL;DR: In this paper, a Ti-47Al-2Cr-2Nb (at.%) material was fabricated using two laser-based methods, Selective Laser Melting (SLM) and Direct Metal Deposition (DMD), for potential uses in aircraft jet engines.
Abstract: A Ti-47Al-2Cr-2Nb (at.%) material was fabricated using two laser-based methods, “Selective Laser Melting” (SLM) and “Direct Metal Deposition” (DMD), for potential uses in aircraft jet engines. Experiments were conducted under controlled atmosphere by changing the processing parameters. Optimal parameters were searched for this relatively low ductility material to prevent cracking due to built-up residual stresses during fast cooling. It was observed that these non-equilibrium cooling conditions were fast enough to generate ultra fine and metastable structures exhibiting high microhardness values. Post heat-treatments were successfully used to restore homogeneous lamellar or duplex microstructures and to relieve the residual stresses. A comparison of these two methods is provided in terms of powder requirements and of process parameters to achieve noncracked structures and fully dense materials.
69 citations
TL;DR: A combined reaction of hydration and carbonation takes place in hydraulic lime and lime-pozzolana mortars as discussed by the authors, and the degree and the order of these reactions are strongly influenced by the moisture content.
Abstract: A combined reaction of hydration and carbonation takes place in hydraulic lime and lime-pozzolana mortars. Hydration reactions are the first reaction and carbonation of lime is the complementary reaction in the strength gain. Competition between these two reactions can occur in lime-pozzolana mortars if the pozzolanic material has low reactivity with lime, leading to the consumption of lime by carbonation reaction. The degree and the order of these reactions are strongly influenced by the moisture content. Hydration reactions are enhanced under moist conditions while carbonation is delayed. Curing under dry conditions does not sufficiently increase their strength because the hydration reactions are slowed down or even terminated by the full carbonation of lime in lime-pozzolana mortars. The consequence of this on the mechanical properties of the mortars is remarkable while the same impact is not observed in their porosity. Such mortars require moist conditions to ensure sufficient strength development.
69 citations
TL;DR: In this article, polymer films of rice starch/Polyvinyl alcohol (PVA) were prepared by casting method and different blends were made varying the concentration of Rice starch and PVA.
Abstract: Polymer films of rice starch/Polyvinyl alcohol (PVA) were prepared by casting method. Different blends were made varying the concentration of rice starch and PVA. Tensile strength (TS) and elongation at break (Eb) of the prepared films were studied. Films made up of rice starch and PVA with a ratio of 2:8 showed highest TS. 10% sugar was added with highest TS giving four composition of Starch/PVA blend in order to increase TS and Eb. Films made up of rice starch and PVA and sugar with a ratio of 1:8:1 showed highest TS and Eb and the recorded value was 14.96MPa and 637% respectively. The physico-mechanical properties of the prepared sugar incorporated films were improved by grafting with acrylic monomer with the aid of UV radiation. A formulation was prepared with monomer, methylmethacrylat in methanol, and a photo initiator. The highest TS of the grafted films were recorded and the value was 16.38 MPa. The water uptake and weight loss in both soil and water of the grafted films are lower than the non-grafted films. The prepared films were further characterized with stereo micrograph and XRD. Finally, the produced film can be used as biodegradable packaging materials for shopping and garbage bags that are very popular and environment friendly.
68 citations
TL;DR: In this paper, a solution graft copolymerization of natural guar gum (GG) with partially neutralized acrylic acid (NaA) using ammonium persulfate (APS) as initiator and N,N′-methylenebisacrylamide (MBA) as crosslinker was investigated.
Abstract: Utilization of natural polymer as matrix for preparing hydrogels can improve the performance of the materials and render them environmentally friendly. In this work, the guar gum-g-poly(sodium acrylate) (GG-g-PNaA) superabsorbent hydrogels were prepared by the solution graft copolymerization of natural guar gum (GG) with partially neutralized acrylic acid (NaA) using ammonium persulfate (APS) as initiator and N,N′-methylenebisacrylamide (MBA) as crosslinker. FTIR spectra confirmed that NaA had been grafted on GG chains. The effects of reaction variables including the concentration of APS and MBA, the weight ratio of acrylic acid (AA) to GG and the neutralization degree of AA on water absorption were investigated. The superabsorbent hydrogel prepared under optimal condition gives the best absorption of 1107 g∙g–1 in distilled water and 88 g∙g–1 in 0.9 wt% NaCl solution. Effects of external pH on the swelling properties of hydrogels were investigated, and the practical water retention properties of the hydrogels were also evaluated. Results indicated that the hydrogels exhibited excellent pH-stability in a wide pH range from 4 to 11, and the water-retention capabilities of sand soils were also greatly improved after utilizing the superabsorbent hydrogels. This superabsorbent hydrogels could be used as potential eco-friendly water-saving materials for agricultural or ecological application.
67 citations
TL;DR: A space–time autoregressive integrated moving average (STARIMA) model to predict the traffic volume in urban areas achieves a very good accuracy on the 5 minute interval forecasting and provides a sufficient accuracy of 30minute interval forecasting compared with ARIMA model.
Abstract: The paper proposes a space–time autoregressive integrated moving average (STARIMA) model to predict the traffic volume in urban areas. The methodological framework incorporates the historical traffic data and the spatial features of a road network. Moreover, the spatial characteristics in a way that reflects not only the distance but also the average travel speed on the links. In order to response the time-varying speed, six traffic modes are classified by level of service (LOS) which is updated in 5 minute interval. In the end, with the real traffic data in Beijing for experiments, the model achieves a very good accuracy on the 5 minute interval forecasting, it also provides a sufficient accuracy of 30 minute interval forecasting compared with ARIMA model.
57 citations
TL;DR: In this paper, a series of titania nanoparticles was successfully synthesized via sol gel method using titanium tetraisopropoxide as a precursor using x-ray diffraction and scanning electron microscopy (SEM).
Abstract: A series of titania nanoparticles was successfully synthesized via sol gel method using titanium tetraisopropoxide as a precursor. In this paper, data concerning the effect of pH towards the development of TiO2 nanoparticles is reported. The samples were characterised by x-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). XRD results showed the existence of nanocrystalline anatase phases with crystallite size ranging from 7-14 nm. Surface morphological studies obtain from SEM micrograph showed the particles with rodlike shape are rutile while the spherical shapes are anatase in nature. It was also found the pH of the solution affect the agglomeration of the particles. Results of photocatalytic studies exhibits that titania powder prepared at pH 9 has an excellent photocatalytic activity with degradation 74.7% within 60 minutes.
51 citations
TL;DR: In this paper, the authors used volume-standar to design four kinds of matrix asphalt mixture, fulfilled mechanics performances and performances of semi-flexible pavement material with different aging, compared with common asphalt mixture and researched the effect by air void and pore structure.
Abstract: The volume parameter of matrix asphalt mixture is an important target in the design of the semi-flexible pavement. The research used volume-standar to design four kinds of matrix asphalt mixture, fulfilled mechanics performances and performances of semi-flexible pavement material with different aging, compared with common asphalt mixture and researched the effect by air void and pore structure. It proves that the compacted intensity, high-temperature stability and low temperature bend of the semi-flexible pavement material is better than common asphalt pavement material, the performances of matrix asphalt mixture with high air void is better. As for matrix asphalt mixture with same air void but different pore structure, the performances of homogenous grade design is prior to consecutive grade disign.
49 citations
TL;DR: In this paper, the authors describe five push-out tests carried out at the University of Malaya using channel shear connector and propose an equation for the shear capacity of these connectors in normal and light weight aggregate concrete.
Abstract: This paper describes five push-out tests carried out at the University of Malaya using channel shear connector. The tests study experimentally and analytically, the behavior of channel shear connectors embedded in normal and light weight aggregate concrete (LWAC). Limited push-out tests are used to measure the accuracy of a proposed nonlinear finite element model for typical push-out test specimens. Using this model, an extensive parametric study performed to arrive at prediction for shear capacity of channel connectors in LWAC. An equation is suggested for the shear capacity of these connectors in LWAC.
48 citations
TL;DR: The paper describes the methodology proposed in the PERPETUATE Project, which uses a displacement-based approach for the vulnerability evaluation and design of interventions, and develops European Guidelines for evaluation and mitigation of seismic risk to cultural heritage assets.
Abstract: The paper describes the methodology proposed in the PERPETUATE Project (funded by the Seventh Framework Programme – Theme ENV.2009.3.2.1.1). The methodology proposed in PERPETUATE uses a displacement-based approach for the vulnerability evaluation and design of interventions. The use of safety verification in terms of displacement, rather than strength, orients to new strengthening techniques and helps in the comprehension of interaction between structural elements and unmovable artistic assets. The procedure is based on the following fundamental steps: definition of performance limit states, specific for the cultural heritage assets (considering both structural and artistic assets); evaluation of seismic hazard and soil-foundation interactions; construction knowledge (non-destructive testing, material parameters, structural identification); development of structural models for the seismic analysis of masonry structures and artistic assets and design of interventions; application and validation of the methodology to case studies. Two main scales are considered: the seismic risk assessment at territorial scale and at the scale of single historic building or artistic assets. The final aim of the project is to develop European Guidelines for evaluation and mitigation of seismic risk to cultural heritage assets.
TL;DR: In this paper, the analysis of the seismic response of masonry building aggregates for a better understanding of the vulnerability of single structural units and of their behaviour within the aggregates is presented.
Abstract: The work focuses on the analysis of the seismic response of masonry building aggregates for a better understanding of the vulnerability of single structural units and of their behaviour within the aggregates. Idealized representative models are developed based on the typical characteristics of the row conglomeration typology. The seismic response of the models is evaluated and discussed by means of nonlinear dynamic analyses.
TL;DR: In this article, the mineralogical components of palm oil fuel ash (POFA) with or without unburned carbon by using semi-quantitative X-ray diffraction (XRD).
Abstract: The purpose of this paper is to investigate the mineralogical components of palm oil fuel ash (POFA) with or without unburned carbon by using semi-quantitative X-ray diffraction (XRD). Original POFA taken from palm oil mill was ground in ball mill, producing ground POFA (GPOFA). Unburned carbon was removed by heating the GPOFA at 500 °C for 1 h, producing treated POFA (TPOFA). Neither glassy phase crystallization nor agglomeration of GPOFA particles occurred during the heat treatment. The content of crystalline phase and glassy phase in GPOFA or TPOFA was determined using semi-quantitative XRD analysis internal standard method. The results showed that GPOFA and TPOFA contained 67.22% and 73.89% of glassy phase, respectively, which could be used as pozzolanic materials. The presence of P2O5, K2O and Na2O in POFA was the reason of reducing the melting point of POFA in boiler.
TL;DR: In this paper, the measurement of in-plane micro-deformation of foil is of great importance for understanding and predicting its thermal, hydroscopic and mechanical behaviour during processing.
Abstract: Flexible electronics technology can potentially result in many compelling applications not satisfied by the rigid Si-based conventional electronics. Commercially available foils such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) have emerged as the most suitable polymer materials for wide range of flexible electronics applications. Despite the enormous progress which has been recently done on the optimization of physical and mechanical properties of PET and PEN foils, their dimensional stability at the micro-scale is still an issue during patterning of wiring by means of lithography. Consequently, the measurement of in-plane micro-deformation of foil is of great importance for understanding and predicting its thermal, hydroscopic and mechanical behaviour during processing. © (2010) Trans Tech Publications.
TL;DR: In this article, a 3D nonlinear finite element models were conducted for CFSST column and steel beam connection under monotonic load using ABAQUS software to identify the modes of beam failure and joint shear failure and the effect of an extra shear plate welded to beam web inside the column was investigated.
Abstract: Recent studies show that a through beam connections composed of concrete filled square steel tubular column and steel beam have been identified as an ideal rigid connection. In this paper a 3-D nonlinear finite element models were conducted for CFSST column and steel beam connection under monotonic load using ABAQUS software. Each model includes a CFSST column and single steel beam passing through the column. The main scopes are to identify the modes of beam failure and joint shear failure. In addition the effect of an extra shear plate welded to beam web inside the column was investigated. This result can be used for designing of through beam connection.
TL;DR: In this paper, a three-dimensional transient thermal finite element model has been developed in Fused Deposition Modeling (FDM), where the moving material of ABS by the sprayer on the mold equipment is simulated with the employment of ANSYS parametric design language (APDL) and latent heat is considered by using enthalpy.
Abstract: Taking into account temperature-dependent thermal conduction and heat capacity, based in the research on the physical property of the material of Acrylonitrile Butadiene Styrene (ABS), a three-dimensional transient thermal finite element model has been developed in Fused Deposition Modeling (FDM). The moving material of ABS by the sprayer on the mold equipment is simulated with the employment of ANSYS parametric design language (APDL) and latent heat is considered by using enthalpy. By the technique of element live and die on ANSYS software and using the nonlinear finite element method, several conclusions according to the simulation results were produced, first of all, the simulation result shows that the temperature field distribution likes an ellipse; secondly, comparing with the previous track, the latter one has larger heat affected region and larger inhomogeneous temperature distribution; the greatest temperature gradient takes place near the edges of deposited part where the sprayer scanning direction changes.
TL;DR: In this article, the application of Phase Change Material (PCM) to asphalt mixture can lighten the temperature-dependent disease of the asphalt pavement and improve the usability as well as extend the operating life of it.
Abstract: The application of Phase Change Material (PCM) to asphalt mixture can lighten the temperature-dependent disease of the asphalt pavement and improve the usability as well as extend the operating life of it. We choose agreeable PCM with comprehensive consideration to the technical requirement of its application in the construction industry and the characteristic of asphalt mixture. Through simulating temperature experiment, we make a conclusion that incorporate the carrier accompanied PCM into asphalt mixture can reduce the increasing rate and cooling rate of the mixture, which shows that PCM can put into use of adjusting the asphalt mixture operating temperature, softening the negative influence of ambient temperature variation on asphalt mixture.
TL;DR: The NiCoFeCrAl3 high entropy alloy coating with a little addition of C, Si, Mn, Mo has been succesively synthesized by laser cladding as discussed by the authors.
Abstract: The NiCoFeCrAl3 high entropy alloy coating with a little addition of C, Si, Mn, Mo has been succesively synthesized by laser cladding. The results show that simple solution phases of ordered BCC and a small fraction of FCC are obtained with fine equaixed dendrites morphology. Because the fine grain strengthening obtained by rapid solidification and the additived small atomic elements like C, Si further increase the distortion of the solid solution lattice, The microhardness of the coating reached above 800 HV and is 50 % higher than previous study on the similar composition by arc melting technique.
TL;DR: In this paper, coupon tests were conducted to investigate the mechanical characteristics of basalt FRP (BFRP) sheet, basalt-carbon hybrid FRP sheets and the corresponding epoxy rein under the effect of freeze-thaw cycling.
Abstract: Coupon tests were conducted to investigate the mechanical characteristics of basalt FRP (BFRP) sheet, basalt-carbon hybrid FRP sheets and the corresponding epoxy rein under the effect of freeze-thaw cycling. FRP sheets and epoxy rein coupons were subjected to up to 200 and 250 freeze-thaw cycles respectively. Test parameters included the number of freeze-thaw cycles and the types of FRP composites. Test results show that (1) BFRP sheet perform better than CFRP or GFRP sheets under high freeze-thaw cycles; (2) exposed hybrid FRP sheets not only show very little loss in mechanical properties, but also contribute to the stability of test data; (3) mechanical properties of rein epoxy decrease significantly with increasing freeze-thaw cycles.
TL;DR: In this paper, a low-permeability condition was considered and the best injection volume of SiO2 nano-powder under the low permeability conditions was selected, and the injection pore volume and injection concentration were obtained.
Abstract: SiO2 nano-powder is a new type of augmented injection agent, has the ability of stronger hydrophobicity and lipophilicity, and can be adsorbed on the rock surface so that it changes the rock wettability. It can expand the pore radius effectively, reduce the flow resistance of injected water in the pores, enhance water permeability, reduce injection pressure and augment injection rate. Using artificial cores which simulated geologic conditions of a certain factory of Daqing oilfield, decompression and augmented injection experiments of SiO2 nano-powder were performed after waterflooding, best injection volume of SiO2 nano-powder under the low-permeability condition was selected. It has shown that SiO2 nano-powder inverted the rock wettability from hydrophilicity to hydrophobicity. Oil recovery was further enhanced after waterflooding. With the injection pore volume increasing, the recovery and decompression rate of SiO2 nano-powder displacement increased gradually. The best injected pore volume and injection concentration is respectively 0.6PV and 0.5%, the corresponding value of EOR is 6.84% and decompression rate is 52.78%. According to the field tests, it is shown that, in the low-permeability oilfield, the augmented injection technology of SiO2 nano-powder could enhance water injectivity of injection wells and reduce injection pressure. Consequently, it is an effective method to resolve injection problems for the low-permeability oilfield.
TL;DR: In this paper, the microstructure of Rene N4 alloy layers produced by laser cladding on oriented CMSX-4 single crystal substrates was analyzed in the solidification condition after different temperature/time ageing cycles in order to assess the possibility of improving high temperature strength of laser deposited superalloys.
Abstract: In this paper, results concerning the microstructure of Rene N4 alloy layers produced by laser cladding on oriented CMSX-4 single crystal substrates are presented. The microstructure of the deposits was analyzed in the solidification condition after different temperature/time ageing cycles in order to assess the possibility of improving high temperature strength of laser deposited superalloys. The present work demonstrates that single crystalline deposits of Rene N4 nickel superalloy can be obtained provided that the deposition direction and the processing parameters are properly selected. The clad layer is perfectly bonded to the substrate and presents no pores or cracks. The deposits grow epitaxially on the substrate, so they inherit its orientation. For laser beam powers and scanning speeds varying between 500 to 800 W and 4 to 12 mm/s, respectively and (001) substrates, the deposited material presents a columnar dendritic structure consisting of arrays of similarly oriented dendrites, separated by subgrain boundaries, forming a single crystal. Heat treatments effective for the dissolution of detrimental phases and for inducing the precipitation of cuboid ’-Ni3Al strengthening phase precipitates in the laser clads were established.
TL;DR: The strain Bacillus sp.
Abstract: The strain Bacillus sp. WD23 exhibiting laccase activity was screened from forest soil. The M9 medium containing Cu2+ was used for enriching and isolating bacterial strains capable of oxidizing syringaldazine (SGZ). One isolated strain was identified as Bacillus subtilis WD23 based on the results of physiological and biochemical tests and 16S rDNA sequence analysis. The strain WD23 could grow at temperatures ranging from 20 to 55°C and showed optimum growth temperature and pH at 25°C and 7.0, respectively. The sporulation rate of the strain clearly correlated well with the laccase activity. The temperature half-life of the spore laccase was 2.5 h at 80°C and the pH half-life was 15 d at pH 9.0. Its spore laccase could decolorized 50~90% of Remazol brilliant blue R (RBBR), alizarin red, congo red, methyl orange and methyl violet, which suggests the potential application of spore laccase in dyestuff treatment.
TL;DR: In this article, the effects of peak ampere, pulse on time and pulse off time on tool wear rate (TWR) of titanium alloy Ti-6Al-4V in EDM utilizing copper tungsten as an electrode and positive polarity of the electrode.
Abstract: Electrical discharge machining (EDM) is relatively modern machining process having distinct advantages over other machining processes and able to machine Ti-alloys effectively. This paper attempts to investigate the effects of peak ampere, pulse on time and pulse off time on tool wear rate (TWR) of titanium alloy Ti-6Al-4V in EDM utilizing copper tungsten as an electrode and positive polarity of the electrode. A mathematical model for electrode wear rate is developed in this paper. Design of experiments method and response surface methodology techniques are implemented. The validity test of the fit and adequacy of the proposed models has been carried out through analysis of variance. It can be seen that as the peak current increases the TWR decreases till certain ampere and then increases. The excellent surface finish is investigated in this study at short pulse on time and in contrast the long pulse duration causes the lowest TWR. Long pulse off time provides minimum TWR and the impact of pulse interval on TWR depends on peak current. The result leads to wear rate of electrode and economical industrial machining by optimizing the input parameters.
TL;DR: In this paper, the electrical resistivities (ρ), compressive stresses (σ), and longitudinal strains (el) of cured nanocomposites under cyclic uploading/unloading were simultaneously collected, to characterize their stress/strain-sensitive properties.
Abstract: Cement-based nanocomposite filled with only 0.1 wt.% multi-wall carbon nanotube (MWNT) (MNFRC), or hybrid with 0.1 wt.% MWNT and 0.5 wt.% microsized short carbon fiber (SCF) (SF/MNFRC), were prepared employing surfactant ultrasonic dispersion and high-speed mixing process. The electrical resistivities (ρ), compressive stresses (σ), and longitudinal strains (el) of these cured nanocomposites under cyclic uploading/unloading were simultaneously collected, to characterize their stress/strain-sensitive properties. There exists good piezoresisitivity and high strain sensitivity for MNFRC. The fractional change in ρ (Δρ) regularly descends or ascends following the σ, or the el of MNFRC (the Δρ/el sensitivity near 68). Hybrid of SCF is found to be more effective to improve the self-sensing repeatability and variation stability of the SF/MNFRC rather than the self-sensing sensitivity (the Δρ/el sensitivity only about 64).
TL;DR: In this paper, an environmentally friendly solid acid catalyst, sulfated TiO2 was prepared by precipitation-impregnation method and used to catalyze the production of levulinic acid from cellulose.
Abstract: Using solid acid catalyst for the levulinic acid (LA) production from cellulose is one of the promising methods for utilization of biomass. An environmentally friendly solid acid catalyst, sulfated TiO2 was prepared by precipitation-impregnation method and used to catalyze the production of levulinic acid from cellulose. The concentration of sulphuric acid had a remarkable influence on the construction and catalytic activity of sulfated TiO2. The influence of reaction temperature and catalyst dosage on levulinic acid yield was also investigated with the aim to obtain the highest yield of LA. The optimum condition for the highest yield of levulinic acid (27.2%) was achieved at 240 °C, 0.7g of sulfated TiO2 and reaction time of 15 min. The recycling test indicated that the catalytic activity of the catalyst had a slight decrease after being used two times.
TL;DR: In this paper, a map of the recovery, recrystallization and grain growth in the temperature-time space of TWIP steel samples was obtained, and a phenomenological grain growth equation that is useful for the annealing control of steel was derived from the measurements.
Abstract: Hot rolled, laboratory-cast, TWIP steel samples (5.4 mm thick) of 22% Mn - 0.6% C (in mass-%) were cold rolled to different reductions (from 40 % to 70 %) and subsequently isothermally annealed for various times at temperatures ranging from 450o C to 1100o C. The evolution of recrystallization and grain growth was followed by control of the softening kinetics complemented by metallographic, OIM and microtexture observations. A map of the recovery, recrystallization and grain growth in the temperature-time space was obtained. In all instances, the grain size at the end of recrystallization was very fine, D ≤ 2 µm and larger grain sizes were the result of grain growth. A range of grain sizes 2 µm ≤ D ≤ 50 µm was covered by the grain growth experiments. A phenomenological grain growth equation that is useful for the annealing control of this steel was derived from the measurements.
TL;DR: Using the cross-section angle polishing microscopy, the subsurface damage of the silicon wafers (100) ground by the diamond wheels with different grain size were investigated, and the subsural damage distributions in different crystal orientations and radial locations of the ground wafer were analyzed.
Abstract: Using the cross-section angle polishing microscopy, the subsurface damage of the silicon wafers (100) ground by the diamond wheels with different grain size were investigated, and subsurface damage distributions in different crystal orientations and radial locations of the silicon wafers (100) were analyzed. The experiment results showed that the grain size of diamond wheel has great influence on the subsurface damage depth of the ground wafer. On the ground wafer without spark-out process, the subsurface damage depth increased along the radical direction from the centre to the edge and the subsurface damage depth in crystal orientation was larger than that in crystal orientation; but on the ground wafer with spark-out process, the subsurface damage depth in different crystal orientations and radial locations become uniform.
TL;DR: In this paper, a three dimensional discrete element model is presented as an extension of a previously introduced spatial discrete-element conceived for the simulation of both the in-plane and the out-of-plane behavior of masonry plane elements.
Abstract: The assessment of the seismic response of historical masonry buildings represents a subject of considerable importance but, at the same time, of very difficult task. Refined finite element numerical models, able to predict the non-linear dynamic mechanical behavior and the degradation of the masonry media, require sophisticated constitutive law and a huge computational cost that makes these methods nowadays not suitable for practical application. In the past many authors developed simplified or alternative methodologies that, with a reduced computational effort, should be able to provide numerical results that can be considered sufficiently accurate for engineering practice purposes. However most of these methods are based on simplified hypotheses that make these approaches inappropriate for monumental buildings. In this paper a three dimensional discrete element model, able to predict the nonlinear behaviour of masonry shell elements, is presented as an extension of a previously introduced spatial discrete-element conceived for the simulation of both the in-plane and the out-of-plane behavior of masonry plane elements. The new macro-element enriches a larger computational framework, based on macro-element approach, devoted to the numerical simulation of the seismic behaviour of historical masonry structures.
TL;DR: In this article, a top-down approach has been adopted to synthesize bacterial cellulose nanocrystals, which is found to retain some of the natural properties of native cellulose even in nano-dimensions.
Abstract: Cellulose, the most widespread biopolymer, is known to occur in a wide variety of living species from the worlds of plants and microbial sources like bacteria. Bacterial cellulose produced by Gluconacetobacter xylinus in the form of long fibers can be acid hydrolyzed under controlled conditions to obtain nanocrystals. Such nanocrystals constitute a generic class of ‘green’ nanomaterial and have attained great importance in the field of polymer nanocomposites attributed to their superior properties. However, conventional sulfuric acid hydrolysis route provides cellulose nanocrystals with inferior mechanical and thermal properties. In this study, a hydrochloric acid (HCl) assisted top down approach has been adopted to synthesize bacterial cellulose nanocrystals, which is found to retain some of the natural properties of native cellulose even in nano-dimensions. The morphological parameters were analyzed using atomic force microscopy which confirmed the formation of nanocrystals. Using these novel nanocrystals, poly vinyl alcohol (PVA) nanocomposite films were prepared and characterized for elucidating their properties. The addition of nanocrystals has significantly improved the thermal stability and mechanical properties of PVA nanocomposites. Results of this study demonstrated that nanocrystals obtained by HCl have several advantages in the fabrication of high performance polymer nanocomposite films for food packaging applications.
TL;DR: In this paper, the authors proposed a numerical approach of the hydrogen diffusion process in two-dimensional (2D) situations, e.g. notches, using the weighted residual method to solve numerically the differential equations set out when the geometry was discretized through the application of finite element method.
Abstract: The present work is based on previous research on the one-dimensional (1D) analysis of the hydrogen diffusion process, and proposes a numerical approach of the same phenomenon in two-dimensional (2D) situations, e.g. notches. The weighted residual method was used to solve numerically the differential equations set out when the geometry was discretized through the application of the finite element method. Three-node triangular elements were used in the discretization, due to its simplicity, and a numerical algorithm was numerically implemented to obtain the hydrogen concentration distribution in the material at different time increments. The model is a powerful tool to analyze hydrogen embrittlement phenomena in structural materials.